NASA scrapped its mission to Mars, but undaunted Utah State University engineers linked up with a joint French and Soviet venture to Mars scheduled for 1994 and this week, the teams test their Mars cargo in the Mojave desert.

USU engineers Frank Redd and James Cantrell - in conjunction with other engineers from Cal Tech and USU - developed a metal rope that will be dragged along the surface of Mars by a helium balloon about the size of the Goodyear blimp. Instruments in the rope and the gondola of the balloon will record information about Mars' surface and atmosphere.Redd and Cantrell gave a presentation on the experiment at the Hansen Planetarium Saturday. The men will travel to the Mojave Desert in California this week, where they will meet French scientists who have been developing the balloon that will carry the metal rope.

On Thursday, the French and American scientists will test the balloon and rope together for the first time, Redd said. The engineers selected the Mojave Desert as the test site because it most closely resembles the rock and sand believed to be on the surface of Mars, Cantrell said.

The metal rope - about 3 inches in diameter and 30 feet long - is Cantrell's brainchild. During an undergraduate internship at Cal Tech, Cantrell helped Cal Tech engineers who were struggling to come up with a rope flexible enough to move smoothly through the Mars terrain yet stiff enough not to snag on a rock or crevice.

The rope - called a "snakerope" - consists of metal segments that telescope into each other, Redd said.

Cantrell conceived the idea of designing the metal rope along the lines of the skeleton of a snake, Cantrell said. The preliminary design worked and the USU undergraduate student and his professors suddenly found themselves part of the Mars venture.

Under the international agreement, the Russians will build the spaceship and supervise the nine-month space trip to Mars, Cantrell said. The Soviets will also build the balloon's gondola and be responsible for launching the balloon.

The French have constructed a balloon designed to remain stable during the wide temperature swings on Mars, Cantrell said. The balloon should remain stable in temperatures ranging from minus 300 to 100 degrees Fahrenheit.

The balloon will float high in the Mars skies during the hot daylight hours and sink close enough to the ground at night for the rope to drag along the surface. Engineers are counting on the planet's night winds to blow the balloon across the surface.

The ropes must be able to drag freely along the surface of Mars without snagging, Redd said. If the rope snags, it could pull the balloon to the ground, ending the experiment.

Engineers began working on a design for a rope in 1987. They spent several summers conducting field tests on various prototypes of the snakerope in the desert, refining a design that will protect the sensitive instruments inside and not snag on the surface.

"It's a piece of equipment that pushes the state of the art in every respect," Cantrell said. Cantrell has spent the past six months in France working with French scientists in marrying the rope to the balloon. The rope must also provide a ballast with mass equal to the buoyancy lost by the balloon each evening.

Money from the private Planetary Society provides funding for USU's involvement in the program. The association has spent about $500,000 so far on USU's snakerope, said Louis Friedman, the association's executive director.

The French CNES - France's equivalent of NASA - will spend several million dollars on the balloon and guide rope, Friedman said. The Planetary Society receives its funds from donations and $25 annual dues paid by 130,000 members in 100 countries. The society fosters international cooperation in joint space ventures.